Lidar systems have important applications in an unmanned driving system, for the capability of detecting obstacles in front of the vehicle and providing distance information of the obstacles. Lidar systems often require a high imaging frame frequency, high resolution, long distance measuring capability, small size, high reliability, and low cost.
An exemplary Lidar system may comprise a laser emission system and a detection system. The emitted laser beam by the Lidar system is reflected after encountering a target and is received by the detection system, and the distance of the corresponding target point on the target can be measured based on the laser round-trip time (e.g., by the time flying method). When a whole target area is scanned, three-dimensional imaging of the scanned area can be realized.
Each Lidar system can be classified as a non-coaxial system or a coaxial system, according to whether the optical axes of the emitting optical path and the receiving optical path overlap. In order to ensure that the emitted laser beams all enter the Lidar's receiving field of view after passing through the Lidar blind zone and the transition zone, the emitted laser beams are required to be parallel to the optical axis of the receiving telescope. If the direction of the emitted light beam changes, the Lidar overlap factor correction curve becomes indefinite, and the correct correction results cannot be obtained for the overlap region. When the deviation is so significant that the laser beam deviates from the receiving field of view, the Lidar may fail to detect targets.
In existing Lidar systems, non-coaxial Lidar systems cannot ensure the emitted light beam to be coaxial or parallel to the optical axis of the receiving telescope, due to the deflection of the mirrors, the operating temperature of the semiconductor laser, the vibration of the stage, the replacement wavelength, and the service life of the semiconductor laser. Also, the existing Lidar systems use a one-dimensional rotation of the galvanometer to achieve spatial scanning, which cannot scan an area field of view.